1. Field of the Invention
The present invention relates generally to ink-jet printing technology methods and apparatus and, more specifically, to a method and apparatus for aligning ink-jet pens firing droplets of a clear fluid.
2. Description of the Related Art
The art of ink-jet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, copiers, and facsimile machines employ ink-jet technology for producing hard copy. The basics of this technology are disclosed, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4 (August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No.1 (February 1994) editions. Ink-jet devices are also described by W. J. Lloyd and H. T. Taub in Output Hardcopy [sic] Devices, chapter 13 (Ed. R. C. Durbeck and S. Sherr, Academic Press, San Diego, 1988).
In U.S. Pat. No. 5,635,969 (Allen, assigned to the common assignee of the present invention and incorporated herein by reference), METHOD AND APPARATUS FOR THE APPLICATION OF MULTIPART INK-JET INK CHEMISTRY, a multi-color ink-jet printing system includes a printing element for apply a precisely metered quantity of a colorless precursor to a recording medium surface. The precursor conditions the medium surface prior to application of one or more colorants to the recording medium surface to prevent cockle and curl and to reduce dry time, while conditioning the recording medium surface for uniform dot gain independent of media composition. U.S. patent application Ser. No. 09/069,717, entitled REACTIVE INK SET FOR INK-JET PRINTING, by Askeland et al., and U.S. patent application Ser. No. 09/069,616, entitled MULTI-CHAMBER FLUID SUPPLY, by Askeland et al., and Related Applications cited therein are also assigned to the common assignee of the present invention and are incorporated herein by reference. Hereinafter, clear fluids used to affect ink dry time and permanence and to prevent cockle and curl of the print medium are generically referred to as xe2x80x9cfixers.xe2x80x9d
In U.S. Pat. No. 5,600,350 (Cobbs et al., assigned to the common assignee of the present invention and incorporated herein by reference), MULTIPLE INKJET PRINT CARTRIDGE ALIGNMENT BY SCANNING A REFERENCE PATTERN AND SAMPLING SAME WITH REFERENCE TO A POSITION ENCODER, a method and apparatus for multiple ink-jet print cartridge alignment is provided by scanning a reference pattern and sampling with an optical sensor. In effect, a given test pattern is printed and actual print image data is compared to determine any misregistration of the cartridges. A SYSTEM AND METHOD FOR ESTABLISHING POSITIONAL ACCURACY IN TWO DIMENSIONS BASED ON A SENSOR SCAN IN ONE DIMENSION, also to the common assignee herein and incorporated by reference, is provided in U.S. Pat. No. 5,796,414 (Sievert et al.).
While the method of printing a test pattern and optically detecting actual positions of element of the pattern on the print media provides a valuable tool for colorants that have a sufficient reflectivity difference with respect to the background media, a problem arises with colorants that have a reflectance only a few percent different than the reflectance of the blank media. In U.S. patent application Ser. No. 08/636,439, for SYSTEMS AND METHOD FOR DETERMINING PRESENCE OF INKS THAT ARE INVISIBLE TO SENSING DEVICES (Nelson et al., assigned to the common assignee of the present invention and incorporated herein by reference), a system and method for determining the presence of inks that are visible to the normal human eye, but optically xe2x80x9cinvisiblexe2x80x9d to sensors is provided.
There remains a need for a method and apparatus for aligning an ink-jet print cartridge which prints a clear fluid on the print medium.
In its basic aspects, the present invention provides a method for determining positional correction factors for at least one ink-jet clear fluid writing instrument and at least one ink-jet colorant writing instrument respectively mounted for printing on an adjacently positioned print medium and using a predetermined pattern of printing. The process includes the steps of: mounting the ink-jet clear fluid writing instrument and ink-jet colorant writing instrument in predetermined fixed positions relative to each other for printing pixels on the adjacently positioned print medium; mounting an optical sensing device in a predetermined fixed position relative to the ink-jet clear fluid writing instrument and ink-jet colorant writing instrument; printing a first predetermined pattern in predetermined target regions on a blank print medium by firing from one writing instrument; printing a second predetermined pattern on the print medium by firing from the other writing instrument such that first regions of print occur superjacent the first predetermined pattern and second regions of print occur substantially adjacent the first regions such that the first regions wherein the first and second regions have differences in reflectivity recognizable by the optical sensing device; sensing the first regions and the second regions with the optical sensing device to obtain data representative of the differences in reflectivity; and determining positional difference between the first regions and the second regions compared to predetermined target regions positions of the first predetermined pattern.
In another basic aspect, the present invention provides a test pattern for aligning a clear fixer printhead of a first ink-jet pen firing drops of a clear fixer to a printhead of a second ink-jet pen firing drops of colorant, including: at least one series of positional-calibration indicia of clear fixer formed on a print medium by the first ink-jet pen; and at least one colorant deposited on the series of positional-calibration indicia of clear fixer and on regions of the print medium adjacent to the indicia, wherein the indicia having colorant deposited thereon and the regions of the print medium adjacent to the indicia have different coefficients of reflectivity.
In another basic aspect the present invention provides an apparatus for aligning a clear fixer printhead of a first ink-jet pen firing drops of a clear fixer to printheads of at least one ink-jet pen 115 firing drops of color ink, including: optical sensor devices for projecting light and receiving light to which the clear fixer is optically unrecognizable when deposited on blank print media, wherein the color ink has a reflectivity that is optically recognizable when compared to the blank print media; mechanisms for exposing the print media to the optical sensor while the sensor is operated; a first printhead for printing a predetermined fractional fill pattern on a first region with the first ink-jet pen firing drops of the clear fixer; a second printhead for printing on the print media with color ink from the at least one ink-jet pen firing drops of color ink both superjacent onto the fractional fill pattern and region adjacent the fractional fill pattern on the blank print media such that bleed of the clear fixer with the superjacent color ink converts the fractional fill pattern in to a fill pattern that has a different reflectivity than the regions adjacent the fractional fill pattern; and mechanisms for comparing data representative of the predetermined fractional fill pattern to the actual position of the first region.
In another basic aspect the present invention provides an ink-jet pen hard copy apparatus for depositing droplets of marking fluid on targeted pixels of a print media, including: a first printing mechanism for printing a clear fluid on a print medium in a print zone of the apparatus; a second printing mechanism for printing ink on the print medium in the print zone of the apparatus; a determining mechanism for determining presence of print on the print medium, including an optical sensing means for directing light onto the print medium and detecting reflections of the light from the print medium wherein the determining means senses reflectivity differences between ink on the print medium and ink overlaid on the clear fluid on the print medium; and a positioning mechanism for locating particular regions of patterns printed by the first printing means and second printing means, the patterns having both regions of ink on the print medium and regions of ink overlaid on the clear fluid on the print medium.
It is an advantage of the present invention that it provides a method and apparatus for optically determining deposits of clear fluid without resorting to ultraviolet, infrared, flourescent, or the like specialized mechanisms for sensing.
It is an advantage of the present invention that it provides a solution that does not require additional components to be incorporated into an ink-jet hard copy apparatus.
It is another advantage of the present invention that by using existing product devices, manufacturing costs are not increased.
It is another advantage of the present invention that by using existing product devices it reduces the potential of added complexity and attendant lowering of reliability.
It is another advantage of the present invention that it permits the manufacture of products having a minimized size.
It is another advantage of the present invention that it provides a product adaptable to a plurality of functional designs.
Other objects, features and advantages of the present invention will become apparent upon consideration of the following explanation and the accompanying drawings, in which like reference designations represent like features throughout the drawings.